JPS6132742B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drive device for a turntable in a disc player, and in particular, a slit or a through hole is provided at a position corresponding to the disc size of the turntable, and light passing through the slit or the like is controlled. The present invention relates to a device that obtains a switching signal in response to an interruption, and uses this switching signal to reliably detect the presence or absence of a disk on a turntable or the size of the disk.

Generally, the presence or absence of a disk or the size of the disk is detected in this way and the motor is driven, or following the lead-in of the tone arm.
Switching the control means for determining the stylus drop-in point is implemented in some known disk players. As a means for detecting the presence or absence of a disk or the disk size, a method has been proposed in which a photoelectric conversion means that does not apply a load to the turntable is associated with the rotation of the turntable. To explain this simply by looking at Figure 1,
A turntable 4 is supported on a center shaft 3 that is integrally provided with the shaft 2 of the motor 1.
A lamp 5 is disposed on one side of the turntable 4, and photoelectric conversion elements 6, 7, and 8 are disposed on the other side in accordance with the size of the disk to be loaded on the turntable 4. Through holes 9, 1 are formed in the disc body of the turntable 4 corresponding to the conversion elements 6, 7, 8.
0 and 11 are drilled. Then, depending on the size of the disk placed on the turntable, the optical path of one of the through holes 9, 10, 11 is blocked, and the photoelectric conversion elements 6,
Based on the selective switching information generated by the irradiation of the light beams 7 and 8, a signal processing circuit formed of, for example, a logic circuit detects both the presence and size of the disk, and detects, for example, the tone arm. Select the drop-in point of the stylus following the lead-in.

By the way, if the through holes or slits 9, 10, 11 formed in the turntable 4 are extremely small in size, the photoelectric conversion elements 6, 7, 8 will be affected by the effects in relation to the rotational speed of the turntable 4. Since the amount of incident light is small, detection errors often occur. For example, as shown in Fig. 2, even if the center angle of the slit 12 formed in the turntable 4 is widened to 30 degrees, when the turntable 4 rotates 45 times, light will pass through the slit 12. The time is about 0.1 seconds, so in order to ensure that the photoelectric conversion elements 6, 7, and 8 operate within this short time, it is necessary to use a light source with a large capacity or to further expand the slit 12. However, it is unfavorable in terms of performance and appearance.

In view of these conventional drawbacks, the present invention
In the first stage of rotationally driving the turntable 4, it is operated at low speed and a small capacity light source from a small slit is transmitted to the photoelectric conversion elements 6, 7,
A novel turntable driving method in which the turntable 4 is rotated at a predetermined constant speed at a stage after the disk size is detected as described above. This is a proposed circuit.

The following is a circuit diagram showing an embodiment of the present invention and a time chart of signals in each part of the circuit.
I will explain in detail.

First, 20 is a generator attached to a servo motor, and voltage dividing resistors 21, 22, and 23 are connected in series on the output side of the generator.
The connection point of 2 and the connection point of resistors 22 and 23 are 1
It is connected to two fixed side contacts a and b of a circuit two-contact type relay switch 24. In addition, 20
r is the internal resistance of the generator 20. Reference numeral 25 denotes a level detection transistor, the base side of which is connected to the movable contact side c of the relay switch 24, the emitter connected to the ground side, and the collector connected to the base of the motor rotation speed control transistor 26. ing. Note that 27 is a capacitor for smoothing the detection output of the transistor 25, and 28 and 29 are a thermistor and a Zener diode, respectively, which are connected together with a parallel resistor 30 and a series resistor 31 between the collector and emitter of the transistor 25 to prevent temperature changes. In response to this, the base input of the transistor 26 is controlled to be constant. 32 is the input resistance of the power source _B1 .

On the other hand, the collector of the transistor 26 and the power supply
Between B ₂ and the player's start switch 3
3, a parallel circuit of a motor 34 and a capacitor 35 is connected. Also, 36 and 3
Reference numeral 7 denotes a power supply voltage detection resistor, the middle point of which is connected to the base of the relay control transistor 38, and the connection between the base and ground determines the time at which the relay starts operating together with the detection resistors 36 and 37. A capacitor 39 is connected. 40 is a relay to which a surge killer diode 41 is connected.

Next, to explain the circuit operation with this configuration, first, the start switch 33 of the player
When the relay switch 24 of the relay 40 is open, the movable contact c of the relay switch 24 is connected to the fixed contact a, and the rotation of the motor 34 is also stopped. Next, when the start switch 33 is closed, the motor 34 receives the power supply _B2 and is driven to rotate through the transistor 26. Further, due to the rotation of the motor 34, a voltage appears at the output terminal of the generator 20, and this appears to be divided by the resistors 21, 22, and 23.

On the other hand, when the start switch 33 is closed, a predetermined voltage divided by the dividing resistors 36 and 37 is supplied to the base of the transistor 38; A charging current flows through the capacitor 39 for the time set by the time constant circuit, and the voltage at the end of the capacitor 39 gradually rises, but in this transient state, the relay 40 is disconnected. Not energized. Therefore, the movable contact c of the relay switch 24
remains connected to the fixed contact a side, and the electromotive voltage of the generator 20 is supplied to the base of the transistor 25 via the resistor 21 (here,
Ignoring the resistance value of generator 20r, resistors 21, 22, 2
3 are respectively R ₁ , R ₂ , and R ₃ , then the base potential of the transistor 25 is e ₀ (R ₂ +
R ₃ )/(R ₁ +R ₂ +R ₃ )), the transistor 2
The impedance of the transistor 5 decreases, lowering the base potential of the transistor 26, and the impedance between its collector and base increases, causing the motor 34 connected thereto to rotate at a low speed.

However, when the capacitor 39 is charged and the base potential of the transistor 38 becomes high and becomes steady, the transistor 38 is turned on and therefore the relay 40 is energized. As a result, the movable contact c of the relay switch 24 is switched to the fixed contact b side, and the voltage applied to the transistor 25 drops (at this time, the base potential of the transistor 25 is e ₀ R ₃ /(R ₁ +R ₂ +R ₃ ), the impedance increases and the above power supply B ₁
A large current flows into the base of the other transistor 26, lowering its impedance,
A relatively large current flows through the motor 34 to rotate the motor 34 at a predetermined high speed. That is, after the relay 40 is energized, the motor 34 is switched from low speed drive to high speed drive. Therefore, the resistor 22 is made adjustable and the resistor 21 is selected to an appropriate value so that the motor 34 reaches a standard rotational speed when the movable contact c is connected to the fixed contact b. If this is done, the motor 34 can be rotated at a low speed when it starts up, and after the time constant has elapsed, the rotation speed can be switched to the specified rotation speed. FIG. 4 is a time chart of signals in each part of the circuit. In this case, the time T required for the motor 34 to start rotating from low speed to high speed is sufficient if the turntable rotates approximately once. Note that the switching signal can also be obtained when the magnetic head is placed facing the magnet attached to the turntable, and in this case as well, the switching signal can be detected reliably.

As described above, the present invention provides a disk size detector comprising a light emitting element, a plurality of light receiving elements arranged at positions corresponding to through holes formed in a turntable on which the disk is placed, and A motor for driving a table, and a time constant means provided in a control circuit for controlling the rotational speed of the motor, the motor is rotated at a low speed within a predetermined time by the time constant means, and the disc size detector is detected by the disk size detector. Since the disc size is detected and the motor is rotated at a predetermined high speed after the predetermined time has elapsed, the disc size can be easily and reliably detected by rotating the turntable.

[Brief explanation of the drawing]

Figure 1 is a partially cutaway front view of a device that detects the size of a disc placed on a turntable;
3 is a plan view showing another embodiment of the turntable, FIG. 3 is a diagram of an embodiment of a circuit including the gist of the present invention, and FIG. 4 is a time chart of signals in various parts of the circuit. 1...Motor, 4...Turntable, 5...
Light sources constituting the switching means, 6, 7, 8...
...a photoelectric conversion element constituting the switching means,
9, 10, 11...Through holes constituting switching means, 36, 37, 39...Time constant means.

Claims (1)

[Claims] 1. A disk size detector comprising a light emitting element and a plurality of light receiving elements arranged at positions corresponding to through holes drilled in a turntable on which the disk is placed; A driving motor is provided, and a time constant means provided in a control circuit for controlling the rotational speed of the motor, the motor is rotated at a low speed within a predetermined time period by the time constant means, and the disk size detector detects the disc size. A drive device for a turntable, characterized in that the size is detected and the motor is rotated at a predetermined high speed after the predetermined time has elapsed.